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LAngband is a written in Common Lisp. It is distributed under the GNU General
Public License (GPL). LAngband has been designed to be a roguelike engine
where you can write and/or customise your own variant/plugin which will not
interfere or ruin other code. To do this it uses the powerful object-oriented
features of Common Lisp (e.g multi-methods and generic functions) as well as
the functional features which allows the engine to treat user-code (classes,
functions, ...) as first-class objects and not just ad-hoc add-ons.